The cover says this book is "genre-bending". The search for the missing father could arguably make it a mystery. That they are being hunted down by a shadowy organization might qualify it as "adventure/espionage". But, there was not enough focus on these aspects, not enough tension or excitement on the page, for me to put it in either category. To me, it felt like most of the book was just there to set up the "payoffs" which come at the end.

One such "payoff" for readers of this novel is seeing how the two timelines are tied together and which characters appear in both. Another, hinted at by the title, is getting to see someone who makes subtle (and only sometimes reasonable) modifications to Wikipedia pages get the opportunity to make some subtle alterations to actual history.

As for what makes this "mathematical fiction", many characters in both historical periods are mathematicians. We are also led to believe that some mathematical discovery lies behind the music box's special abilities. However, a brief reference to "spirals" and "higher dimensional spaces" did not give me any reason to believe that a wooden box with springs and gears that plays a tune could cause people to travel through time, and so it still just seemed like a "magic music box" to me. This may not be the reaction of most readers, but I would have appreciated more mathematical details.

Interestingly, the author explains in the acknowledgments that some of the characters and events in this book were based on her grandfather's memoir Reminiscences of the Vienna Circle and the Mathematical Colloquium.

Despite the famous warning against judging a book this way, my favorite thing about The Expert of Subtle Revisions is the way its cover looks like the Wikipedia entry for itself.